1. Technical Field
The present invention relates to an electronic device that has a multi-layer body in which a first substrate and a second substrate are joined to each other by a joining resin portion composed of a photosensitive resin, a liquid ejecting head, and a method of manufacturing the electronic device.
2. Related Art
The electronic device is a device that is provided with driver elements such as piezoelectric elements or the like that deform by application of a voltage and has been applied to various liquid ejecting apparatuses and pressure/vibration sensors and the like. For example, in a liquid ejecting apparatus, various liquids are ejected from a liquid ejecting head that uses the electronic device. As liquid ejecting apparatuses, for example, there exist image recording devices such as ink jet printers, ink jet plotters and the like, however, recently, liquid ejecting heads have been applied to various manufacturing devices by utilizing their advantage of being able to make a minute amount of liquid precisely land onto a designated position. For example, liquid ejecting heads have been applied to display manufacturing devices that manufacture color filters of liquid crystal displays and the like, electrode forming devices that form electrodes of organic electroluminescence (EL) displays, field emission displays (FEDs) and the like, and chip manufacturing devices that manufacture biochips. In addition, a recording head for image recording devices ejects liquid ink, and a color material ejection head for display manufacturing devices ejects solutions of individual color materials of red (R), green (G), and blue (B). Moreover, an electrode material ejecting head for electrode forming devices ejects a liquid electrode material and a bioorganic matter ejecting head for chip manufacturing devices ejects a solution of bioorganic matter.
The above-described liquid ejecting heads include an electronic device in which a pressure-chamber-forming substrate formed of pressure chambers that communicate with nozzles, piezoelectric elements (a type of driver element) that cause a change in pressure in the liquid inside the pressure chambers, a sealing plate (also called a protective substrate) that is arranged so as to be separated at a distance from the piezoelectric elements, and the like are stacked. An electronic device in which such substrates are bonded together so as to form a space therebetween that houses a piezoelectric element has been proposed (for example, JP-A-2002-86724). In addition, in a semiconductor package in micro-electro-mechanical systems (MEMS) such as various sensors, a structure is adopted in which substrates are stacked and joined by using joining resin portions in order to achieve densification and size reduction of wiring. The joining resin portions are patterned in a predetermined shape on a substrate through a photolithography process, that is, through processes such as coating onto a substrate, pre-baking (pre-curing), exposure, development and post-baking (main-curing).
In recent years, size reduction and densification of liquid ejecting heads has progressed, and it has become difficult to secure a joining width (joining surface of adhesive) necessary to join substrates to each other. In this regard, in the invention disclosed in JP-A-2002-86724, on the side of the substrate (the (110)-oriented silicon substrate) that is the side joined to the other substrate having a piezoelectric element, a dividing wall that defines a space that houses the piezoelectric element, is formed so as to become triangular in cross section by performing anisotropic etching in such a manner that the width of the dividing wall becomes narrower toward the piezoelectric element side. The leading end of the dividing wall is pushed against a highly elastic layer and fixed thereto by pressure-joining. Consequently, the dividing wall does not interfere with the piezoelectric element and a space that houses the piezoelectric element is defined.
However, in the above-described configuration, even though a dividing wall is formed by performing anisotropic etching on the silicon substrate, there is a problem in that the degree of freedom for the dimensions and shape of the dividing wall are limited and further size reduction and densification of the liquid ejecting head and the electronic device are difficult.